Second alpine lake field season is over

30 September marked the end of the long field season for the brook trout (Salvelinus fontinalis) eradication program conducted within the framework of the BIOAQUAE project. Intensive fish capture operations, commenced in the summer of 2013, were resumed in early June 2014 after the winter break.

In the course of the second field season, GPNP researchers spent the entire summer in the Park, living in the local structures, and obtained some encouraging results. In particular, they believe the eradication process in the two smaller lakes included in the project (Lago Nero and LakeDjouan) was completed earlier than expected (Fig.1). Several thousand fish were captured in Lake Dres, but they mostly consisted of young specimens (only 10 of the fish captured in 2014 were longer than 15 cm), which, consistently with the indications provided in the research project, could not be captured during the first year of the program on account of their extremely small size (Fig.2). In the Leynir lake, the largest and deepest, capture rates dropped to extremely low levels, even though a few hundred fish, comprised of young and adult specimens, were captured during the 2014 field season (Fig 2).

Biodiversity recovery has been progressing at an unexpected pace. In particular, some groups of macro invertebrates (aquatic insects such as caddis flies) are thriving in the lakes treated.

On the whole, the results of the second field season have been satisfactory and give reason to hope for the future of brook trout eradication activities.

The brook trout eradication operations are nearing completion at Lago Nero and Lake Djouan. During the winter, 32 fish were captured in Lake Djouan and none in Lago Nero. During the summer season, no fish were captured in Lake Djouan and only 4 fish, ca 9 cm long, were captured in Lago Nero. On the X-axis: number of days elapsed since the start of the eradication operations; on the Y-axis; number of fish captured per session.

The number of fish captured at the Dres Lake continued to be high in 2014: 1600 in the winter (of which only 2 were potential reproducers) and about 3500 in the summer months (of which less than 10 were potential reproducers). At the Leynir Lake 300 fish were captured in the winter and ca 600 in the summer (with a few dozen potential reproducers). In both lakes capture rates have dropped appreciably. On the X-axis: number of days elapsed since the start of the eradication process; on the Y-axis; number of fish captured per session.

The first season of LIFE+ BIOAQUAE project concluded successfully

Autumn has come, and with it the first season of fieldwork for the eradication of brook trout (Salvelinus fontinalis) from the alpine lakes of the Gran Paradiso National Park has come to an end. The eradication of this non-native trout is one of the initiatives undertaken under a three-pronged plan, the LIFE+ BIOAQUAE project. Based on the satisfactory results obtained so far, prospects look good for the recovery of these high elevation aquatic ecosystems.

The first season of LIFE+ BIOAQUAE project concluded successfully

In order to eradicate this introduced species originating from North America, an aggressive predator whose presence has greatly undermined the biodiversity of the alpine lakes, LIFE+ BIOAQUAE researchers placed tens of fishing nets in each of the 4 lakes included in the eradication program. Fishing activities went on continuously for over three months (from June through September), resulting in the removal of ca 8000 fish and a sharp drop in fish population density in the lakes.

The chart on the right shows the typical catch rate for brook trout as recorded in the Djouan Lake in Valsavarenche: the high number of fish caught during the first few days declined fast and the rate stabilised over values close to zero as the fieldwork season progressed.

The results obtained indicate that the eradication methods employed (fishing nets and electrofishing) work well for this type of intervention, which will be carried on in the coming years. The good news is that a few timid but significant signs of ecosystem recovery may already be discerned. Dozens of dragonflies are flying over the Dres Lake in Orca Valley and Daphnias are swimming in the pelagic zone; for the first time, some Dytiscidae(tiny swimming Coleoptera) have been seen in the Nero Lake in Valsavarenche, while in the Djouan Lake, in the same valley, frogs are back in great numbers and quite a few caddisflies are managing to survive.

The five-year project is still in its early stage, but the return of some of the autochthonousspecies to the alpine lakes is a positive sign that engenders enthusiasm and confirms the importance of this action. During the long alpine winter, while the fishing nets continue their slow work of capturing the fish beneath the frozen surfaces of the lakes, the researchers will conduct laboratory analyses on the samples collected. In the spring of 2014, a new eradication drive will get underway, and it is hoped will provide further evidence of the efficacy of this action.

Glossary

Eradication: removal of a species from a location, in this case, removal of brook trout from the alpine lakes.

Introduced species: a species non-native to a site, which has been transported to the new location either directly or indirectly by human activity; also referred to as allochthonous species.

Progress report

The LIFE+ BIOAQUAE officially started on the first September 2012. Currently, the first season of the exotic fish eradication action from some alpine lakes in the park, the planning of the phytodepuration systems in the two projected sites and the planning of the fish incubator for the marble trout, are being completed.

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